The present invention is to a universal closed-loop, electrical stimulation system which may be integrated with a multi-channel electromyography (EMG) and/or body position sensors (such as, angle accelerometers and gyroscopes) to allow for 1) real-time measurement of body position and movement, 2) autonomous system configuration utilizing closed-loop control and multi-channel capacity, 3) direct operation of neural and muscular structures in the human body and, 4) user-friendly programming capabilities. The electrical stimulation system may produce a variety of electrical outputs such as functional electrical stimulation (FES), transcutaneous electrical nerve stimulation (TENS) and neuromuscular electrical stimulation (NMES). For convenience, the term FES will be used herein to refer to these different electrical stimulation types. The closed-loop FES system of the present invention can also be integrated with wearable garments in its use or combined with electromagnetic devices to deliver further benefits to users.
FES is a method, undergoing continuing development, to restore function to patients with damaged or destroyed neural pathways with microprocessor controlled electrical neuromuscular stimulation and can be used with or without an orthotic device. FES systems use electronics to generate electrical impulses. These impulses are transcutaneous, typically transferred through surface electrodes to stimulate contraction/activity of the muscles that are otherwise dysfunctional or not operating optimally. In order for useful and controlled movements of limbs to be achieved several muscles must usually be operated in concert and sensory feedback closed-loop control is required to alter stimulation patterns in real-time. The impulse delivery is normally coordinated by an algorithm executed under the control of the FES system, the end result being the delivery of a patterned and timed stimulation sequence.
FES systems can be used as an assistive device for neural prostheses to restore functions lost because of neural damage. FES facilitates neuromodulation to help restore motor functions and sensory functions. For example, FES can be used to enhance the function of upper and lower limbs in individuals with paralysis related to spinal cord injury (SCI) or stroke. It has been used to allow standing, walking, cycling, grasping, bowel-and-bladder control, male sexual assistance, and respiratory control in individuals with paralysis related to central nervous system disease (i.e. spinal cord disease (SCD), multiple sclerosis (MS), traumatic brain injury (TBI), spinal cord injury (SCI)). Traditionally, in any nervous system (brain or spinal cord) disease that allows for the (partial) preservation of the nerve pathway to the muscle, FES can be considered to improve either organ anatomy (i.e. muscle mass) or function (i.e. bladder evacuation).
Damage to the mammalian central nervous system (“CNS”) can produce devastating physical impairment (paralysis) and associated medical complications and co-morbidities that are life-threatening. Paralysis directly affects most of the organ systems in the body:
a) respiratory system is affected by decrease lung volumes and decreased ability or inability to take a volitional breath.
b) cardiovascular system is affected by the inability to regulate the blood pressure and heart rate.
c) autonomic nervous system is affected and leads to difficulty in regulating body temperature.
d) gastrointestinal and genitourinary systems are affected by the inability to voluntarily control bowel movements and urination. In addition, sexual function is also significantly impaired, to the point of total loss of function.
e) musculo-skeletal system is impaired to volitionally control movement or control abnormal movements. For example, trunk weakness after spinal cord injury leads to trunk instability which further leads to poor posture, difficulty doing activities of daily living (ADL) and a primary contributing factor to the development of upper limb pain and injury.
The use of FES to restore motor function in individuals with neurological impairments is a technique used widely in both clinical practice and paralysis related research institutions. To date however there are very few commercial FES systems that are fully integrated remote systems that adjust stimulation based on sensory feedback in an effort to optimize performance.
As stated, FES has been used to restore certain functions following neural injury or disease. Examples include enhancing the function of the upper limbs in individuals with paralysis related to spinal cord injury (SCI) or stroke, restoring standing, walking and cycling in individuals with paralysis related to central nervous system disease (i.e. spinal cord disease (SCD), multiple sclerosis (MS), traumatic brain injury (TBI), cochlear implants for restoration of hearing, stimulation of muscles and peripheral nerves to restore motor function including hand grasp and release, breathing, and bladder emptying; and deep brain stimulation to treat the motor symptoms of Parkinson's disease (Grill, Warren M., Kirsch, Robert F., “Neural Prostheses”, Wiley Encyclopedia of Electrical and Electronics Engineering, 27 Dec. 1999). Each of these applications work by stimulating neural activity in intact neuromuscular systems to restore control to systems where control has been compromised by injury or disease. FES therapy and neural prostheses devices have also been used with or without locomotor training, such as on a treadmill, or cycle training for individuals with motor paralysis to restore or improve walking. A neural prosthesis device consists of a microprocessor-based electronic stimulator with one or more channels for delivery of individual pulses transcutaneously. The device may also be integrated with a mechanical brace.
An algorithm, that may be stored and controlled by the FES microprocessor, activates channels to stimulate peripheral nerves and trigger muscle contractions to produce functionally useful movements that allow patients to sit, stand, walk, and grasp. Closed-loop FES devices are systems, which provide feedback information on muscle activity and/or joint position, thus allowing constant modification of stimulation parameters, which are required for complex activities such as walking. These are contrasted with open-loop systems where an electronic stimulator only controls the output without considering feedback information.
FES devices have also been developed for patients with foot drop. Foot drop is weakness of the foot and ankle that causes reduced dorsiflexion and difficulty with ambulation. It is often a result of damage to the central nervous system such as stroke, incomplete spinal cord injury, traumatic brain injury, cerebral palsy and multiple sclerosis. Stimulation of the peroneal nerve has been used as an aid in raising the toes during the swing phase of ambulation. Examples of such devices used for treatment of foot drop are the Innovative Neurotronics (formerly NeuroMotion, Inc.) WalkAide®, Bioness radio-frequency controlled NESS L300™, and the Odstock Foot Drop Stimulator.
FES can assist standing and primitive walking in SCI individuals has been achieved utilizing the Parastep® Ambulation System. Using this system, only spinal cord injury patients with lesions from T4 to T12 were considered candidates for ambulation as the energy requirements for the individuals with higher injuries were considered prohibitive and individuals with lower neurologic injuries would not respond to the electrical stimulation parameters utilized by the Parastep. Using percutaneous stimulation, the device delivers trains of electrical pulses to trigger action potentials at selected nerves at the quadriceps (for knee extension), the common peroneal nerve (for hip flexion), and the paraspinals and gluteals (for trunk stability). Patients use a walker or elbow-support crutches for further support. The electrical impulses are controlled by a computer microchip attached to the patient's belt that synchronizes and distributes the signals. In addition, there is a finger-controlled switch that permits patient activation of the stepping. Other devices added a reciprocating gait orthosis (RGO) to an FES system but the orthosis used was a cumbersome hip-knee-ankle-foot device linked together with a cable at the hip joint and the use of this device was limited by the difficulties in putting the device on and taking it off (Hirokawa, Gimm, Le, Solomonow, Baratta, Shoji, D'Ambrosia, “Energy Consumption in Paraplegic Ambulation Using the Recipriocating Gait Orthosis and electrical stimulation of thigh muscles”, Arch Phys Med Rehabilitation 1990 August; 71(9):687-94). Neuromuscular stimulation is also proposed for motor restoration in hemiplegia and treatment of secondary dysfunction (e.g., muscle atrophy and alterations in cardiovascular function and bone density) associated with damage to central motor nerve pathways.
Despite the described devices, a great need therefore remains for universal, closed-loop, portable, easy to use interchangeable and multi-functional systems that partially or completely restore lost or impaired motor and sensory function in individuals suffering from disruptions of motor and sensory function due to damage of the CNS. The commercial market translation of surface FES systems has been limited in capability and scope. Surface FES systems for general clinical use are limited to 2-4 channel open-loop systems or simple biofeedback closed-loop systems (e.g. NeuroMove™ NM900 and Thought Technology MyoTrac Infiniti). FES cycling uses knowledge from the machine itself (e.g. crank angle and/or cadence) to adjust the timing of muscle activation. A few commercial products have coupled movement sensors such as accelerometers and gyroscopes in a closed-loop fashion with surface FES, but they have limitations, such as for example, Innovative Neurotronics WalkAide which has 1 FES channel and 1 accelerometer. Bioness NESS L300 has 1 FES channel and 1 foot switch. There are a few commercial products that provide multi-channel movement sensors but not in combination with FES (Delsys Trigno Wireless). There are few patents and no closed-loop products that currently target trunk function in SCI. What is needed to improve clinical care and evidence-based user outcomes is a smart multi-channel, 3D position sensor and/or EMG regulated, closed-loop FES system that can automate stimulation (i.e. smart system) to maximize physical reconditioning and spontaneous neurological recovery with the capacity to be used in a clinical center, gym or home-based environment while being monitored at a distance.
Discovery of new control approaches, which can exploit voluntary movements to drive the body in an intended way, has been of great interest to scientists and clinicians. Electromyographic signals have been investigated to a large extent as a means to predict the level of muscle activation for performing activity or adjusting stimulation upon sensing fatigue. Moreover 3-D movement sensors to automate stimulation signals have been used in several studies (Williamson R and Andrews B J, “Sensor systems for lower limb functional electrical stimulation (FES) control”, Med Eng Phys 22: 313-325, 2000; Simcox S, Parker S, Davis G M, Smith R W and Middleton J W, “Performance of orientation sensors for use with a functional electrical stimulation mobility system”, J Biomech 38: 1185-1190, 2005). Patented invention approaches include (U.S. Pat. No. 7,346,396 Barriskill et al., U.S. Pat. No. 7,162,305 Tong et al.). Despite the substantial evidence that automating stimulation is more effective than using manual methods in a variety of rehab applications, real-time closed-loop FES control of patient parameters is not widely available to clinicians.
Therefore, a need exists for a universal closed-loop FES system that would measure, monitor, stimulate and provide sensory feedback closed-loop real-time control for the human nervous system. This can be used in sports and fitness for motion capture and analysis; toning, tightening and strengthening muscles; and cardiovascular exercise. It can also be used for people with paralysis strengthening muscles, nerves and restoring motor and sensory function. Scientifically this system can be used to validate outcome measures in SCI related to research. Currently, trunk function assessment in SCI individuals is significantly limited by the inability to perform a detailed clinical examination. There is no current tool to objectively assess the trunk muscle activity. Without a valid and practical means to measure the neurologic function between T2-T12, assessing the safety and efficacy of potential therapeutic interventions in humans will seriously be hampered. Creating a critical outcome assessment tool for thoracic spinal cord function will have the largest impact on future human clinical trials, rehabilitation strategies, and understanding the physiologic basis (neuroplasticity) for activity-based restorative therapies (ABRT).